Hydrocarbons in the Solar Nebula

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Science  16 Mar 2001:
Vol. 291, Issue 5511, pp. 2049
DOI: 10.1126/science.291.5511.2049a

Recent studies of interplanetary dust particles and primitive meteorites have identified hydrocarbons in the samples; sometimes these phases were associated with iron and nickel metal. These organic materials must have formed in the solar nebula, but how they did has been unclear. The solar nebula (the flattened disk of debris left over from the formation of the sun) contained abundant gases—carbon monoxide and hydrogen—and dust grains—iron metal and refractory oxide phases—which swirled around the sun and either aggregated into planetesimals or were removed from the disk.

Fischer-Tropsch catalysis is the conversion of CO and H2 into simple hydrocarbons by an iron or nickel metal catalyst, and Kress and Tielens have modeled this known surface chemical reaction to try to determine the origin of simple hydrocarbons in the solar nebula. They found that Fischer-Tropsch catalysis could have served to convert CO into CH4 at the time of planetesimal formation. At earlier times, the temperatures would have been too high, and at later times the temperatures too low, for catalysis to be efficient. Thus, their kinetic model offers a plausible route for hydrocarbon formation in the solar nebula and may help provide clues to organic material origins in other astrophysical environments. — LR

Meteorit. Planet. Sci.36, 75 (2001).

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